Wat is the green smudge in this galaxy? Could this be a #voorwerp or is it an error in the color filter? Visible in all layers. In SDSS the smudge has a blue color. Nothing in Simbad Search.

Ine :stars::dizzy:


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Well that’s very odd. At first glance, you’d have to say either voorwerp or weird artifact. It appears in multiple single exposures, so i’d say probably a real astrophysical effect. Whether it’s a voorwerp or not, I couldn’t say for sure, but the galaxy does have infrared excess, so is likely an AGN, which makes voorwerp a definite possibility.

One for the GZ thread I think!


Idk I think this is like one of the coolest things I’ve seen on here… right next to a radio ring galaxy too…


So did Ine discover an unpublished Voorwerp?

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It could be an imbalance between the exposures of the colour filters that make up the image?
The g filter has an exposure time of 500s, the r filter about 160s and the z filter about 340s.
Contrast this with another galaxy elsewhere that has exposure times g=360s, r=230s and z=530s and which looks more normal.

If it’s a voorwerp, the other filters wouldn’t necessarily detect it. Depends on the specific ionization mechanism but they tend to be pretty narrow band I think.

We do exposure-balance the bands – ie the images are basically scaled to intensities (like counts/second through clear skies). So very long exposures don’t change the overall colors, but they make the images less noisy (cleaner looking / less staticky).

(In fine detail, that’s not quite true because there is a non-linear color stretch, so if you take a noisy patch of sky and zoom out, the overall color may be different than a cleaner patch of sky, because the positive and negative noise pixels don’t exactly cancel out because of the nonlinearity.)

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So, it’s a real green hue then?

" :musical_score: The chances of anything coming from Mars are a million to one, they said … :notes:"

Yeah I think the ionization mechanism is usually OIII doubly ionized oxygen plasma from the astrophysical jet. Well to me it looks like its more prominent in the r band actually? Now I don’t know what the R band is for SDSS, or how redshift necessarily works with these bands, but I think it would have to be .1 redshift for OIII emission-5007 angstrom-to show up mainly in the r band?


My pennyworth is that it’s a consequence of a sudden burst of hot massive young short-lived stars. High energy radiation is absorbed by obscuring gas and dust clouds, so what we see is emission spectra from the clouds radiating energy at longer wavelengths, the green OIII. What has caused this sudden outburst?

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